Portable computer system

Abstract: A computer system is provided that employs a disable technique which warns the user of a low battery condition when the user attempts to power-on the computer, and which prevents power from being applied to a primary portion of the computer system. A battery monitor is included for monitoring the voltage across the battery, and for asserting a control signal when the battery voltage drops below a certain threshold value. A control unit receives the control signal and accordingly prevents power from being applied to a primary computer subsystem when the computer system is turned on. Instead, when the user attempts to turn on the computer system when the low battery-capacity condition exists, the control unit causes a pulse generator to generate a signal that drives a speaker. An audible indication of the low power condition is thereby produced. In accordance, the user is alerted to the low battery condition, while further power is prevented from being depleted from the battery as a result of applying power to the primary computer subsystem.

Description: This invention relates to portable computer systems and more particularly to low battery detection and indicator circuitry for portable computer systems. It is frequently desirable to warn the user of a portable computer system of a condition when the battery capacity is low. Accordingly, a variety of battery monitors and so-called "fuel gauges" have been developed that provide an external indicator of a low battery-capacity condition. These external indicators include both LED indicators and visual displays incorporated on the computer screen. The battery monitors may indicate when the battery capacity, as inferred by the voltage across the battery, decreases below a certain threshold, or may indicate the capacity of the battery over a broad range of possible values. In portable computer systems, if the battery capacity is diminished to a critical point, damage to the battery and other system components may occur. If the computer is powered-on, the user may receive the indication of the low battery condition in real time and may accordingly power-down the system to recharge the battery. If, on the other hand, the computer is in a powered-off state or in a power-conserving suspend state (during which, for example, the CPU clock signal and the system clock signal may be stopped), the user may be unaware of a law battery condition. Thus, if the user subsequently attempts to turn on the computer system or the system attempts to restart the CPU and system clock signals, the battery will be drained even further. This can damage the battery and other system components. Examples of power-conserving power management systems for portable computers are disclosed in our co-pending patent applications published as EP-A-0,656,579, EP-A-0,645,690 and EP-A-654,726. Another such example is in EP-A-565,914 which discloses minimising power consumption by collecting and interpreting power related data at various processing elements while hiding many of the details from the end-user. The present invention is directed to the problem mentioned above when a user attempts to turn on the computer from a powered-off state and is unaware of a low battery condition. According to the present invention there is provided a portable computer system comprising: a primary computer subsystem; a battery pack; a user activated power switch coupled between said battery pack and said primary computer subsystem for providing power from said battery pack through said power switch to said primary computer subsystem; a battery monitor unit for monitoring the capacity of said battery pack and capable of generating a control signal indicative of a low battery condition; and a control unit coupled to said battery monitor unit, wherein said control unit prevents power from being provided to said primary computer subsystem through said power switch when said control signal is asserted, and wherein said control unit generates an indicator signal for activating a user indicator when said control signal is asserted and when said power switch is closed by the user. BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the accompanying drawings in which: Figure 1 is a block diagram of computer system that employs a disable technique according to the present invention. Figure 2 is a waveform diagram that illustrates a signal provided from a pulse generator for producing an audible indication of a low battery condition. Figure 3 is a schematic diagram of a control unit employed within the computer system of Figure 1. Referring now to the drawings, Figure 1 is a block diagram of a portable computer system 10 that employs a disable technique during low battery conditions according to the present invention. In the embodiment of Figure 1, computer system 10 includes a battery pack 12 coupled to a battery monitor unit 14 and a power switch 16. A control unit 18 is coupled to battery monitor 14 and to power switch 16. Control unit 18 includes a pair of output lines, one of which is coupled to a pulse generator 20 and the other of which is coupled to a primary computer subsystem 22. A speaker 24 is finally shown coupled to pulse generator 20. Primary computer subsystem 22 is representative of a variety of major functional subunits of computer system 10. For example, in the preferred embodiment, primary computer subsystem 22 includes a system microprocessor, a system memory, and a system display, among other things. During normal operation of computer system 10 when the battery cells that comprise battery pack 12 are completely charged, power is provided to the primary computer subsystem 22 through power switch 16 and control unit 18. In one embodiment, the nominal voltage produced by battery pack 12 is 12 volts. When battery pack 12 is fully charged, battery monitor unit 14 detects the nominal voltage at an input line and accordingly deasserts (low) an indicator signal labeled "VLBATT". When the indicator signal VLBATT is deasserted low, control unit 18 allows battery power to be coupled to the primary computer subsystem 22 when power switch 16 is closed. If, while power switch 16 is closed and primary computer subsystem 22 is powered-on, the voltage V b across battery pack 12 falls below a certain predetermined threshold value, battery monitor unit 14 asserts the indicator signal VLBATT. Control unit 18 responsively prevents power from being applied to primary computer subsystem 22 and generates a control signal that is received by pulse generator 20. In response to this control signal, pulse generator 20 produces a pulsed signal, as illustrated in the waveform diagram of Figure 2. The pulsed signal generated by pulse generator 20 drives speaker 24, which accordingly produces an audible tone. It is noted that in the embodiment of Figure 1, the pulse signal generated by pulse generator 20 induces a beeping sound consisting of three 1 second tones. If, on the other hand, the capacity of battery pack 12 diminishes below a certain level when the primary computer subsystem 22 is powered-down, battery monitor unit 14 again detects the low battery condition by monitoring the voltage V b across the battery pack 12. When the battery voltage V b falls below the predetermined threshold value, the battery monitor unit 14 again asserts the VLBATT signal. If the user subsequently attempts to power-on the primary computer subsystem 22 by closing power switch 16 when the VLBATT signal is asserted, control unit 18 prevents power from being applied to the primary computer subsystem 22. When the power switch 16 is closed, the control unit 18 Instead provides a control signal to pulse generator 20, thereby causing the generation of the pulsed signal (as illustrated in Figure 2) that causes sound to be produced from speaker 24. Figure 3 illustrates one embodiment of control unit 18. The control unit 18 of Figure 3 includes a pair of field effect transistors 30 and 32, an inverter 34, and a one-shot circuit 36. As is evident from the circuit, when the VLBATT signal is deasserted low, transistor 30 is turned on and transistor 32 is turned off. Accordingly, the battery voltage V b is provided to primary computer subsystem 22. When the VLBATT signal is asserted high, transistor 30 is turned off, and transistor 32 is turned on. Accordingly, the battery voltage is disconnected from the primary computer subsystem 22 and one-shot circuit 36 provides a signal to pulse generator 20 that causes the production of an audible indication of the low battery condition. As a result of computer system 10, an external indication of a critically low battery condition of battery pack 12 is provided to the system user even if the primary computer subsystem 22 is powered-down. The external indicator is generated when the user attempts to power the computer system on. Since power cannot be applied to primary computer subsystem 22 when the low battery condition exists, further depletion of battery power is prevented. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. For example, although the computer system 10 of Figure 1 illustrates a pulse generator 20 and a speaker 24 for producing an audible indication of the low battery condition, other indicators that warn the user of the low battery condition may be employed, such as an LED display.

Claims: A portable computer system (10) comprising: a primary computer subsystem (22); a battery pack (12); a user activated power switch (16) coupled between said battery pack and said primary computer subsystem for providing power from said battery pack through said power switch to said primary computer subsystem; a battery monitor unit (14) for monitoring the capacity of said battery pack and capable of generating a control signal VLBATT indicative of a low battery condition; and a control unit (18) coupled to said battery monitor unit, wherein said control unit prevents power from being provided to said primary computer subsystem through said power switch when said control signal is asserted, and wherein said control unit generated an indicator signal for activating a user indicator when said control signal is asserted end when said power switch is closed by the user. The portable computer system as recited in claim 1 wherein said user indicator includes a sound generator (20, 24) coupled to said control unit, wherein said sound generator produces a sound when said indicator signal is provided by said control unit. The portable computer system as recited in claim 2 wherein said sound generator comprises: a pulse generator (20) for generating a pulsing signal; and a speaker (24) coupled to receive said pulsing signal. The portable computer system as recited in any preceding claim wherein said primary computer subsystem includes a microprocessor. The portable computer system as recited in Claim 4 wherein said primary computer subsystem further includes a system memory. The portable computer system as recited in any preceding Claim wherein said battery pack includes a plurality of battery cells. The portable computer system as recited in any preceding Claim wherein said control unit is coupled in series between said power switch and said primary computer subsystem.

Inventors: O'BRIEN RITA M, WISOR MICHAEL T, O'BRIEN, RITA M., WISOR, MICHAEL T.
Applicants: ADVANCED MICRO DEVICES INC, ADVANCED MICRO DEVICES INC.
Application year: 1994
Main classification: G06F1
IPC codes: G06F1